1. Field of the Invention
This invention relates to an air conditioning apparatus for a vehicle, more particularly, relates to an inside/outside air switching unit for the air conditioning apparatus.
2. Description of Related Art
In a conventional air conditioning apparatus, an inside/outside air introduction mode is manually switched by a passenger in a passenger compartment between an entire inside air mode (i.e., inside air circulation mode) and an entire outside air mode (i.e., outside air introduction mode), or is automatically switched according to a cooling load of the passenger compartment. In the automatic control of the inside/outside air introduction mode, the entire inside air mode is automatically selected to improve cooling capacity when the cooling load of the passenger compartment is larger than a predetermined value, and the entire outside air mode is automatically selected to ventilate the passenger compartment when the cooling load of the passenger compartment is smaller than a predetermined value. Further, the cooling load is determined by a target air temperature (TAO) of the passenger compartment. Therefore, the entire outside air mode or the entire inside air mode is automatically selected according to the TAO.
In the recent years, noise from an engine of the vehicle is greatly reduced. Therefore, noise from an air conditioning apparatus is noted by a passenger in a passenger compartment. The noise caused from the engine becomes lower, when a rotation speed of the engine is low (e.g., engine idling), or when the engine is stopped to reduce an exhaust gas even when a passenger is in the passenger compartment. Thus, in this case, air-suction noise of the air conditioning apparatus, which is caused when inside air is sucked from an inside air introduction port in the passenger compartment, is more noted by the passenger in the passenger compartment.